/**
 * Copyright (C) 2007 The AsyncMail Group <asyncmail@googlegroups.com>
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *         http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.googlecode.asyncmail.smtpserver.handler.fastfail;

import java.net.UnknownHostException;

import org.apache.commons.logging.Log;
import org.springframework.beans.factory.annotation.Required;

import com.googlecode.asyncmail.common.DSNStatus;
import com.googlecode.asyncmail.common.MailAddress;
import com.googlecode.asyncmail.dnsservice.DNSService;
import com.googlecode.asyncmail.smtp.SMTPRetCode;
import com.googlecode.asyncmail.smtpserver.SMTPSession;
import com.googlecode.asyncmail.smtpserver.hook.HeloHook;
import com.googlecode.asyncmail.smtpserver.hook.HookResult;
import com.googlecode.asyncmail.smtpserver.hook.HookReturnCode;
import com.googlecode.asyncmail.smtpserver.hook.RcptHook;

/**
 * This hook implementation can be used to reject not resolvable EHLO/HELO
 */
public class ResolvableEhloHeloHandler implements RcptHook, HeloHook {

    public final static String BAD_EHLO_HELO = "BAD_EHLO_HELO";

    protected DNSService dnsServer = null;

    private Log logger;

    @Required
    public void setLogger(Log logger) {
        this.logger = logger;
    }

    @Required
    public void setDnsService(DNSService dnsServer) {
        this.dnsServer = dnsServer;
    }

    /**
     * Check if EHLO/HELO is resolvable
     * 
     * @param session
     *                The SMTPSession
     * @param argument
     *                The argument
     */
    protected void checkEhloHelo(SMTPSession session, String argument) {
        if (isBadHelo(session, argument)) {
            logger.debug("HELO/EHLO " + argument + " invalid");
            session.getState().put(BAD_EHLO_HELO, "true");
        }
    }

    /**
     * @param session
     *                the SMTPSession
     * @param argument
     *                the argument
     * @return true if the helo is bad.
     */
    protected boolean isBadHelo(SMTPSession session, String argument) {
        // try to resolv the provided helo. If it can not resolved do not
        // accept it.
        try {
            dnsServer.getByName(argument);
        } catch (UnknownHostException e) {
            return true;
        }
        return false;

    }

    /**
     * @see com.googlecode.asyncmail.smtpserver.hook.RcptHook#doRcpt(com.googlecode.asyncmail.smtpserver.SMTPSession,
     *      org.apache.mailet.MailAddress, org.apache.mailet.MailAddress)
     */
    public HookResult doRcpt(SMTPSession session, MailAddress sender,
            MailAddress rcpt) {

        if (session.getState().containsKey(BAD_EHLO_HELO)) {
            return new HookResult(HookReturnCode.DENY,
                    SMTPRetCode.SYNTAX_ERROR_ARGUMENTS, DSNStatus
                            .getStatus(DSNStatus.PERMANENT,
                                    DSNStatus.DELIVERY_INVALID_ARG)
                            + " Provided EHLO/HELO "
                            + session.getConnectionState().get(
                                    SMTPSession.CURRENT_HELO_NAME)
                            + " can not resolved.");
        } else {
            return new HookResult(HookReturnCode.DECLINED);
        }
    }

    /**
     * @see com.googlecode.asyncmail.smtpserver.hook.HeloHook#doHelo(com.googlecode.asyncmail.smtpserver.SMTPSession,
     *      java.lang.String)
     */
    public HookResult doHelo(SMTPSession session, String helo) {
        checkEhloHelo(session, helo);
        return new HookResult(HookReturnCode.DECLINED);
    }

}
